Depends on where you want to go and what you want to do.

Christmas Day in particular has very little open (shops or attractions), but public transport still runs and hotel restaurants should be open (perhaps reduced hours).

Boxing day, new years day and day after new years everything that a tourist uses will be open.

The main cities will be fairly empty over this period, and conversely holiday areas (beaches, lakes) will be packed (most likely all accommodation was sold out months ago).